ORIGIN OF THE WOODY MACARONESIAN SEMPERVIVOIDEAE AND THE PHYLOGENETICPOSITION OF THE EAST-AFRICAN SPECIES OF AEONIUM

Evolutionary relationships among the genera of Macaronesian Sempervivo ideae, Aeonium, Aichryson, Greenovia, and Monanthes, were studied usin g sequence variation of the chloroplast DNA trnL (UAA) - trnF(GAA) spa cer and the nuclear ribosomal Internal Transcribed Spacer 2 (ITS2). Ph ylogenetic analysis indicates that the Moroccan Sedum sect. Monanthoid ea is the sister taxon of the Macaronesian Sempervivoideae. In combina tion with the terminal position in the Macaronesian Sempervivoideae of the East African A. leucoblepharum, which has formerly been assumed t o be the sister taxon of the other species of Macaronesian Sempervivoi deae (i.e. Aichryson and Monanthes), a recent remigration to Africa is suggested. Statistical support for the terminal position of A. leucob lepharum using only spacer sequences is without homoplasy but not high since only single mutations in both the chloroplast and nuclear seque nce characterize the clade containing A. leucoblepharum. A. leucobleph arum and the Canarian species with a similar growth-form share 50% of the RAPDs. Within a clade comprising woody species with yellow flowers and a herbaceous rosette, the highest genetic divergence, as determin ed with RAPDs, is found between A. simsii and the woody Macaronesian a nd African species. The extremely close genetic ties among the woody a nd branched (sub)shrubs indicate that, when compared to the other spec ies of the genus, the woody, African Aeonium species are not the siste r group of the Macaronesian Sempervivoideae and substantiate the view that an ancestor of A. leucoblepharum recently migrated from the Canar y Islands to East Africa and Arabia through long distance dispersal, r ather than being a relict of an African Aeonium flora from the Tertiar y.